A beacon attracted attention to a specific location, usually by means of a bright light. For this reason, lighthouses, such as that on Fang Rock, (TV: Horror of Fang Rock) often served as beacons.
The Fisher King used ghosts as beacons to guide his path to the planets he would conquer. (TV: Before the Flood)
On the surface of the storm-plagued planet of Cerberin, there was a radio beacon atop a metal shack. Lucie Miller used the beacon to alert the Eighth Doctor to the location of her and Elric, the son of a judge who crusaded against interplanetary gangs, one of which the two were desperate to escape. (AUDIO: Flashpoint)
Atop the Great City of the Exxilons was a power draining beacon which drew in energy so that the city could fuel its self-repair. Built too well, the beacon drained power from all technological devices on Exxilon. The beacon was destroyed when an intrusion by the Third Doctor and the Daleks overloaded the city. (TV: Death to the Daleks) When a second wave of the space plague struck, the Dalek Empire constructed a new beacon and affixed it to the ruins of the city. When the humans mining for parrinium, the Daleks activated their beacon. Though the Marine Space Corps quickly destroyed this new beacon, its activation had sufficiently delayed the humans for the Dalek Fleet to intercept them. (AUDIO: The Dalek Protocol) During the Last Great Time War, the Time Lords, studying their records for Dalek weaknesses, dispatched Time Agents in an attempt to contact the Exxilon race at the earlier, more advanced period of their timeline, in the hope that they could provide technical assistance in the construction of a similar power-draining device. (PROSE: Dalek Combat Training Manual)